#app {
  position: relative;
  width: 1000px;
  margin: 0 auto;
}
#app .img-wrap {
  width: 904px;
  height: 408px;
  box-sizing: border-box;
  margin: 0 auto;
}
#app .img-wrap ul li {
  float: left;
}
#app .img-wrap ul li img {
  width: 300px;
  height: 200px;
}
#app .big {
  display: none;
}
#app .big .img-big {
  width: 904px;
  height: 408px;
  margin: 0 auto;
  background-color: #fff;
  opacity: 0.7;
  position: absolute;
  top: 0px;
  left: 50px;
}
#app .big .big-img img {
  width: 500px;
  height: 300px;
  position: absolute;
  top: 50px;
  left: 250px;
}
#app .big .big-img span {
  width: 20px;
  height: 20px;
  background-color: red;
  display: block;
  text-align: center;
  line-height: 20px;
  position: absolute;
  top: 50px;
  right: 230px;
  cursor: pointer;
}
